Dialog system for a man-machine interaction having cooperating dialog devices

ABSTRACT

A system and method for a dialog system which provides for a user to carry on a dialog with dialog experts having different capabilities, during an existing dialog session. A terminal device may be connected to a special switching device, which, in dependence upon a communicated user statement, may provide the user with the optimal system statement from a multiplicity of system statements received from various dialog devices.

FIELD OF THE INVENTION

The present invention relates to a dialog system for a man-machineinteraction, which the user can use to communicate with various dialogexperts.

BACKGROUND INFORMATION

Automated, goal-directed, interactive voice-communication systems orinformation systems operable by natural speech are available, which areable to access databases and which lead the user, through targetedquestions, to desired information, to a transaction or the like. Thedialog is carried out in a very rigid sequence of system questions anduser responses. Examples of such goal-directed interactivevoice-communication systems are, inter alia, telephone banking systemsor card-reservation systems. The goal-directed dialog systems includetargeted querying of the user information necessary for a specificapplication.

However, some users have indicated that systems of this kind are notflexible enough in their current state of development. This is becauseuser statements which are not modeled in the application of theparticular interactive voice-communication system, cannot be interpretedand can lead to irresolvable dialog situations. These irresolvabledialog situations involve the interactive voice-communication systementering into a state where the same text is always output or theconnection is interrupted.

In addition to such goal-directed dialog systems, there are alsoso-called chat dialog systems or ‘chat bots.’ A chat bot gives the userthe impression that the user can carry on a conversation with it aboutnearly any subject. Such a “chat-oriented” dialog system supports a veryfree formulation of questions, responses, and explanations, on the userside, so that a chatty-type dialog can take place between man andmachine. In such a chat-oriented dialog system, any user inputs at allare answered without being rejected. However, a chat-oriented dialogsystem is not suited for conducting a goal-directed informational dialogwhere it is necessary, for example, to query specific user informationbefore the corresponding information can be found and output. For thatreason, chat-oriented dialog systems or chat bots are sometimescriticized by users as not being proficient enough, since neutral andpointless system remarks are sometimes produced in response tonon-modeled user statements. Thus, in some available systems, a user wasonly able to be connected directly and inflexibly to a goal-directeddialog expert or to a chat-oriented dialog expert or chat bot.

SUMMARY OF THE INVENTION

Exemplary embodiments and/or exemplary methods of the present inventionprovide users with a dialog system characterized by greater efficiencyand flexibility.

Exemplary embodiments and/or exemplary methods of the present inventionprovide that a user will no longer have to communicate in a rigid andinflexible manner in a session with one single dialog system. Instead,the user may make contact with a special switching device, which, independence upon his user statement, provides him with the optimal systemstatement from a multiplicity of system statements from various dialogdevices. User and system statements discussed herein may be bothresponses and questions transmitted by a terminal device assigned to theuser or by dialog devices. It can be, therefore, the task of theswitching device to receive a user statement produced by the user, torelay it to a plurality of dialog devices, to wait for the systemstatements from the dialog devices, and, in accordance with a definedlogic, to output the most suitable system statement to the user.

Some dialog devices may be generally available, goal-directed dialogdevices and chat bots, which support an interaction with a user in theform of dialogs. Such dialog devices herein may also be referred to asdialog experts.

Exemplary embodiments and/or exemplary methods of the present inventionprovide a dialog system for a man-machine interaction, which has atleast one terminal device where a user may input a user statement. Theuser statement may be input into the terminal device, for example, byvoice and by using a microphone. It may also be entered via a keyboard.To achieve a high level of user friendliness, the user statement mayalso be entered in natural speech form, i.e., in natural sentences andquestions. However, the manner in which a user statement is entered maynot be essential for the present invention. At least one first switchingdevice may be also provided, which is able to be connected to theterminal device. Assigned to the first switching device may be aplurality of dialog devices, which, in an available manner, are able toreceive, analyze, and process user statements, in order to subsequentlygenerate an appropriate system message. A system message includes asystem statement intended for the terminal device, an identificationcode identifying the particular dialog device, and/or an identifier. Theidentifier may correspond to a hard decision, which, for example, merelysignals to the first switching device whether a dialog device may or maynot generate a system statement in response to a user statement. Theidentifier may also correspond to a soft decision, i.e., it indicateswhich performance or quality a generated system statement has. Thismeans that it indicates the degree to which the generated systemstatement applies to the previously analyzed user statement.

In exemplary embodiments and/or exemplary methods, to be able to offerthe user an optimal dialog, the first switching device may have a firstdevice for relaying a user statement coming from a terminal device to atleast some of the assigned dialog devices, as well as a second device,which, functioning in response to the system messages received from thedialog devices, selects a system message, and transmits the systemstatement contained therein to the terminal device.

In exemplary embodiments and/or exemplary methods of the presentinvention, to be able to communicate an optimized system statement,which may be a system response or a system question, to the user, thesecond device of the first switching device may have a detector devicefor capturing the identifier and the identification code which arereceived in a system message. In addition, a memory device for storing apriority list may be included in the second device. Using the prioritylist and the output signal from the detector device, a decision device,which may be separately designed or integrated with the detector device,may select the system statement of a specific dialog device, in order torelay it to the terminal device. The priority list may contain theidentification codes of each dialog device assigned to the firstswitching device, as well as the priority assigned to the particulardialog device.

In exemplary embodiments and/or exemplary methods of the presentinvention, since the system messages received by the dialog devices maynot be able to be simultaneously processed in the first switchingdevice, for example, because the system messages from various dialogsystems arrive at different points in time, the second device of thefirst switching device may be provided with a memory for storing thereceived system messages or also only the system statements.

In exemplary embodiments and/or exemplary methods of the presentinvention, the decision device may be designed, for example, to applythe identification code of the selected dialog device as a memoryaddress to the memory. This may enable the system statement to betransmitted to the terminal device.

In exemplary embodiments and/or exemplary methods of the presentinvention, to be able to connect the terminal device to dialog devicesof various manufacturers, and various dialog devices to the existingdialog system without substantial outlay, a user interface may beassigned to the terminal device to provide a first communicationprotocol and/or data format for exchanging data with the first switchingdevice. Moreover, each dialog device may have an interface for preparinga second communication protocol and/or data format for exchanging datawith the first switching device. Also, the first device of the firstswitching device may have a conversion device for converting the firstcommunication protocol and/or data format into the second communicationprotocol and/or data format and vice versa.

In exemplary embodiments and/or exemplary methods of the presentinvention, in order to avoid the situation, for example, where a userhas to wait an unreasonable length of time for a response from a dialogdevice, a timer may be provided in the first switching device to monitorthe receipt of a system message within a preset time span. For example,following expiration of the preset time span, the user statement may betransmitted once more by the first switching device to the dialogdevices, or, for example, the first switching device considers only thesystem statements received within the preset time span.

In exemplary embodiments and/or exemplary methods, both the firstswitching device and the dialog devices involved in a correspondingdialog may record the frequency with which their system statements aretransmitted to the terminal device. For this, the first switching devicemay have a confirmation device, for example, which transmits aconfirmation message to the dialog device whose system statement hasbeen relayed to the terminal device. Accordingly, at least some of thedialog devices may have a device for counting and analyzing theconfirmation messages received. In this manner, it may be possible, forexample, that a goal-directed dialog device, which has no longer beenincluded in the dialog for a specific time span, generates a predefined,goal-directed system message, which is switched through by the detectordevice and the decision device in the first switching device, directlyto the terminal device.

In exemplary embodiments and/or exemplary methods of the presentinvention, by recording the frequency with which system statements arerelayed to a dialog device, the priority list may be dynamicallyadapted, during an existing dialog, to the dialog sequence. For example,a dialog device may be assigned a higher priority in the priority listafterwards, when, for example, the system statements of this dialogdevice are relayed very frequently to the terminal device. It is alsopossible that the user himself is able to change the priority list, byinforming the first switching device of the type of dialog desired. Inthis manner, from the outset, a higher priority in the priority list maybe assigned to the appropriate dialog device, in dependence upon thedialog desired by a user.

In exemplary embodiments and/or exemplary methods of the presentinvention, to further optimize the dialog system, a sub-switching devicemay be assigned to each dialog device, it being possible, in turn, for aplurality of sub-dialog devices to be assigned to each sub-switchingdevice. For this purpose, the sub-switching device may have a device,which transmits a user statement relayed by the dialog device, to atleast some of the assigned sub-dialog devices. In addition, a device maybe provided, which, functioning in response to the system messagesreceived by the sub-dialog devices, selects a system message andtransmits it to the first switching device. Following this pre-weightingof system messages, in the manner described above, the first switchingdevice then may select the system message whose system statement is tobe transmitted to the terminal device.

In exemplary embodiments and/or exemplary methods of the presentinvention, the performance and precision of the dialog system may beenhanced by connecting a second switching device between the terminaldevice and a plurality of first switching devices. The second switchingdevice may have a first device for relaying a user statement coming fromthe terminal device to at least some of the first switching devices. Inaddition, a second device may be provided, which functioning in responseto the system messages coming from the first switching device(s), toselect a system message and transmit the system statement containedtherein to the terminal device. In this approach, the first switchingdevice must be designed for relaying a selected system message to thesecond switching device. That is, the first switching device not onlymay transmit the system statement but also may transmit the identifierfrom the dialog device in question that is integrated in the systemmessage and the identification code.

In exemplary embodiments and/or exemplary methods of the presentinvention, the switching devices and/or sub-switching devices may bedesigned to be able to inform the dialog devices or sub-dialog devicesin question, of the dialog end. In this connection, the end of thedialog may be initiated by a specific dialog device, sub-dialog device,or by the user himself, for example, by hanging up the telephonereceiver.

In exemplary embodiments and/or exemplary methods of the presentinvention, the dialog system includes at least one terminal device wherea user may input a user statement. In addition, a plurality ofinterconnectible dialog devices may be provided, which may be connectedto the terminal device. Each dialog device may have a device forreceiving and analyzing a user statement generated by the terminaldevice, as well as a device for generating a system message independence upon the analyzed user statement. Moreover, a decision devicemay be provided for relaying the user statement to another dialog deviceor for relaying a generated system message to the terminal device independence upon the analyzed user statement. For example, the dialogdevices may be connected in series, so that one dialog device alwaysrelays a user statement to the dialog device that follows next when ititself is not able to generate a system message in response to areceived user statement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a dialog system, including a plurality of various dialogexperts, in which the present invention is implemented.

FIG. 2 illustrates another embodiment of a dialog system, in which thepresent invention is implemented.

FIG. 3 depicts another embodiment of a dialog system according to thepresent invention, including dialog experts connected in series.

FIG. 4 shows a basic block diagram of a switching device in accordancewith the present invention, according to FIG. 1.

DETAILED DESCRIPTION

FIG. 1 shows an exemplary embodiment of a dialog system, which, forpurposes of a better and simpler representation, is only shown inextract. Thus, only two terminal devices 10 and 20 are shown, which areeach linked via a user interface 12 or 22 to a subscriber exchange 30.User interfaces 12 and 22 provide a communications protocol and/or dataformat, via which the terminal devices may exchange data with aswitching device 40. For example, terminal device 10 is a telephone, andterminal device 20 a multimodal terminal. Via subscriber exchange 30, auser may establish a connection to switching device 40 by selecting aspecific address. The switching device is described in greater detail inthe following. Assigned to switching device 40 are a plurality ofdifferent dialog experts, of which merely the two dialog experts 50 and60 are shown. In the following description, it may be assumed thatdialog expert 50 is suited for a goal-directed dialog, for example, fora directory assistance, and that dialog expert 60 represents a so-calledchat bot for a chat-oriented dialog.

Dialog experts 50 and 60 each have interfaces 52 and 62, respectively,which provide a specific communications protocol and/or data format forexchanging data with switching device 40.

An exemplary switching device 40 is shown in FIG. 4. Switching device 40has a conversion device 44, which adapts the communications protocoland/or data format between interfaces 52 and 62 of dialog experts 50 and60, respectively, and user interfaces 12 and 22 of terminal devices 10and 20, respectively. This makes it possible for any desired terminaldevices to be connected to any desired dialog experts. In addition,switching device 40 shown in FIG. 4 has a detector device 43, which isprovided for recording system messages that may be generated by dialogexperts 50 and 60. A system message is composed, for example, of theactual system statement intended for a terminal device, anidentification code of the particular dialog expert, and of anidentifier. The identifier may correspond to a hard decision whichmerely signals that the system message includes a system statement. Theidentifier may also correspond to a soft decision, in that it indicatesthe quality of a system statement with respect to an analyzed userstatement. For a hard decision, the identifier may be represented by thebinary digit “0”, i.e., no system statement has been generated, or by a“1”, i.e., a system statement has been generated. When an indication ofthe quality of the system statement is provided, the identifier mayrepresent a number between 0 and 100, in order to define the measure ofthe quality. Thus, for example, number 100 corresponds to a systemstatement which applies optimally to the analyzed user statement.

Detector device 43 may be able to capture the identifier andidentification code of a received system message, and feed them to adecision device 42. In addition, decision device 42 is connected to amemory 46, in which a priority list is stored. In the present example,the priority list includes the identification codes of the two dialogexperts 50 and 60, as well as the priorities assigned to the two dialogexperts. For example, dialog expert 50 enjoys a higher priority thandialog expert 60. Detector device 43 may be linked to a memory 45 inwhich the entire system message or merely the system statement containedin a system message is stored. Decision device 42 is likewise connectedto memory 45, in order to be able to select predefined system statementsto be relayed to a terminal device. To this end, decision device 42 hasa logic, which, in dependence upon the priority list in memory 46 andthe identifier captured in a system message by detector 43, is able todecide whether the system message of dialog expert 50 or of dialogexpert 60 should be relayed to a terminal device. In addition, decisiondevice 42 may generate a confirmation message for the dialog expert,whose system statement has been relayed to a terminal device. Via aswitch 47, the generated confirmation message is placed on the outputline which leads to the appropriate dialog expert.

A control unit 41, which monitors and controls switching device 40, may,for example, log how often a system statement of the two dialog experts50 and 60 has been relayed during a dialog session to the correspondingterminal device.

In addition, dialog experts 50 and 60 may each have a counting andevaluation device 54 and 64, respectively, to determine the frequency ofthe system messages generated by them and relayed to a terminal deviceduring a dialog session with a terminal device. Counting and evaluationdevices 54 and 64 also may assure that a dialog expert is able togenerate a predefined, preferably goal-directed system statement, when,within a preset time span, no more system statement from it has beenrelayed by switching device 40 to a terminal device. This predefinedsystem statement may be immediately switched through by the switchingdevice to the terminal device.

Depending upon how many generated system statements have been relayed bydialog experts 50 and 60 to the particular terminal device, control unit41 may undertake an adaptation of the priority list in memory 46. Shouldit turn out, namely, during a dialog session that the system statementsfrom dialog expert 60 are made available much more frequently than fromdialog expert 50, then, during this dialog session, dialog expert 60 maybe assigned a higher priority than dialog expert 50. It is likewiseconceivable to render possible a user-controlled adaptation of thepriority list for a specific dialog session. If, for example, the usermerely wants to “chat”, and no goal-directed information is needed,then, via his terminal device, he may transmit a control parameter tothis effect to switching device 40, whereupon control unit 41 raises thepriority of dialog expert 60 with respect to dialog expert 50. Thepriority list may also or instead reflect the usage of the participatingdialog experts, the highest priority being assigned to the dialog experthaving the lowest usage. For this purpose, each dialog expert maydetermine his usage and make this available to the assigned switchingdevice. Moreover, the switching exchange itself could estimate the usageof the participating dialog experts on the basis of the correspondingresponse times.

To be able to offer the user a higher dialog quality, a sub-switchingdevice 70 may be assigned to dialog expert 50, and a sub-switchingdevice 80 to dialog expert 60. Three further dialog experts, 90, 191,and 90 are assigned to sub-switching device 70, whereas three otherdialog experts 93, 94 and 95 are assigned to sub-switching device 80. Inprinciple, sub-switching devices 70 and 80 may be designed similarly toswitching device 40. Thus, sub-switching devices 70 and 80 each havedevices 72 and 82, respectively, which retransmit the user statementrelayed by the particular dialog expert 50 or 60 to at least some of theassigned sub-dialog experts 90 through 92 and 93 through 95,respectively. Conversely, the design of sub-switching devices 70 and 80may also include detector and decision devices 74 and 84, respectively,which, functioning in response to the system messages received fromsub-dialog experts 90 through 92 and 93 through 95, respectively, selecta system message and transmit this directly or via assigned dialogexperts 50 or 60 to switching device 40.

FIG. 2 shows another exemplary embodiment of a dialog system which mayoffer a user an improved dialog. Two terminal devices 10 and 20 areconnected, in turn, via corresponding user interfaces 12 and 22,respectively, to a subscriber exchange 30. Subscriber exchange 30 mayconnect terminal devices 10 and 20 to a main switching device 100, whichis connected, in turn, to a plurality of switching devices. To simplifythe illustration, only three switching devices 40′, 40″ and 40′″ areshown. Switching device 40′ is connected, for example, to two dialogexperts 50′ and 60′, switching device 40″ to dialog experts 50″ and 60″,and third switching device 40′″ to dialog experts 50′″ and 60′″. Mainswitching device 100 has a transmission device 102, which relays theuser statement coming from a terminal device to at least some ofswitching devices 40′, 40″ and 40′″. Switching device 40 according toFIG. 1 differs from switching devices 40′, 40″ and 40′″ according toFIG. 2 in that the last-mentioned switching devices not only relay thesystem statement, but the entire system message of a selected dialogexpert, to main switching device 100. To this end, main switching device100 has a detector and decision device 104, which, functioning inresponse to the system messages coming from switching devices 40′, 40″and 40′″, selects an optimal system message and routes the systemstatement contained therein to the corresponding terminal device 10 or20.

FIG. 3 shows another exemplary embodiment of a dialog system, in whichterminal devices 10 and 20 are connected, in turn, via correspondinguser interfaces 12 and 22, respectively, to a subscriber exchange 30. Inaddition, the dialog system has a cascade connection of, for example,three dialog experts 130, 140, and 150, which are able to carry on adialog with terminal devices 10 and 20. Each dialog expert 130, 140 and150 has a receiving and evaluation device 135, 145 and 155,respectively, for receiving and evaluating a user statement generated bya terminal device. Moreover, each dialog expert 130, 140 and 150includes a device 136, 146 and 156, respectively, for generating asuitable system message as a function of the evaluated user statement. Adecision device 137, 147 and 157 is provided in each dialog expert 130,140, and 150. Decision devices 137, 147, and 157 may relay the userstatement obtained from an end device to the following dialog expertwhen it is recognized that the dialog expert in question is not able togenerate a suitable system statement in response to the received userstatement. In addition, decision devices 137, 147 and 157 may be able totransmit a generated system statement to the particular terminal device.It is assumed in the present example that terminal device 10 has beenconnected via exchange 30 to dialog expert 130. It is also assumed thatdialog expert 130 is not able to generate any suitable system statementin response to the user statement coming from terminal device 10, sothat the user statement is relayed to dialog expert 140. Since dialogexpert 140 is able to generate an appropriate system statement, aconnection is established at this point between terminal device 10 anddialog expert 140, and the generated system statement is transmitted toterminal device 10.

It is also noted that all switching devices, sub-switching devices,dialog devices, and sub-dialog devices may be designed for the parallel,i.e., simultaneous handling of dialogs with a plurality of users.

With the aid of the proposed dialog systems, it may be possible toinsert chat-oriented passages within predominately goal-directed dialogsessions, to prevent a dialog from being broken off or ending in adialog loop when a goal-directed dialog expert may no longer be able tomeaningfully respond to a user statement. User statements which lieoutside of the modeled domain of a goal-directed dialog expert, may thenbe handled in the “chatty style”, with the aid of a so-called chat bot.Thus, the possibility is opened up of going beyond the existingtechnological boundaries of the individual dialog experts in auser-friendly way. Overall, therefore, the performance of the proposeddialog systems allows for the ability to handle deviations in userobjectives, and to more successful and user-friendlier dialogs.

1. A dialog system for a man-machine interaction having cooperatingdialog devices, comprising: at least one terminal device, where a userinputs a user statement; at least one first switching device, which isconnected to the terminal device; a plurality of dialog devices, whichare assignable to the at least one first switching device and which,functioning in response to a user statement, are able to generate systemmessages; wherein the at least one first switching device includes: afirst device for relaying a user statement coming from the at least oneterminal device to at least some of the assigned dialog devices of theplurality of dialog devices; and a second device, which, functioning inresponse to the system messages received from the assigned dialogdevices, selects a system message and transmits the system statementcontained therein to the at least one terminal device, wherein thesystem message generated by a dialog device, functioning in response toa user statement, includes a system statement intended for the terminaldevice, an identification code identifying the dialog device, and/or anidentifier, the identifier signals whether or not a system statement hasbeen generated for a terminal device, or what quality the generatedsystem statement has; and the second device of the first switchingdevice has a detector device for capturing the identifier and theidentification code of a system message, a memory for storing a prioritylist of the assigned dialog devices, and a decision device, which, usingthe stored priority list and the output signal from the detector device,selects the system statement of a specific dialog device in order torelay it to the terminal device.
 2. The dialog system as recited inclaim 1, wherein the second device of the at least one first switchingdevice has a memory for storing received system messages.
 3. The dialogsystem as recited in claim 1, further comprising a user interfaceassigned to the at least one terminal device to provide at least one ofa first communication protocol and a first data format for exchangingdata with the at least one first switching device, wherein at least theassigned dialog devices each have an interface for providing at leastone of a second communication protocol and a second data format forexchanging data with the at least one first switching device, and thefirst device of the at least one first switching device has a conversiondevice for converting at least one of: the at least one of the firstcommunication protocol and the first data format into the at least oneof the second communication protocol and the second data format and theat least one of the second communication protocol and the second firstdata format into the at least one of the first communication protocoland the first data format.
 4. The dialog system as recited in claim 1,wherein the at least one first switching device has a timer formonitoring receipt of the system message within a preset time span. 5.The dialog system as recited in claim 1, wherein the at least one firstswitching device has a confirmation device for transmitting aconfirmation message to the assigned dialog device whose systemstatement has been relayed to the at least one terminal device.
 6. Thedialog system as recited in claim 5, wherein at least some of theplurality of dialog devices have a respective counting and analyzingdevice for counting and analyzing received confirmation messages.
 7. Thedialog system as recited in claim 6, wherein functioning in response tothe counting and analyzing devices, the at least some of the pluralityof dialog devices are able to generate a predefined system message, andfunctioning in response to a predefined system message, the detectordevice in the first switching device prompts the decision device totransmit a corresponding system statement to the at least one terminaldevice.
 8. The dialog system as recited in claim 1, wherein the prioritylist stored in the at least one first switching device is modifiable. 9.The dialog system as recited in claim 1, wherein a respectivesub-switching device is assigned to each dialog device of the pluralityof dialog devices and a plurality of sub-dialog devices are assigned toeach respective sub-switching device.
 10. The dialog system as recitedin claim 9, wherein each sub-switching device includes: a transmittingdevice for transmitting the user statement relayed by the assigneddialog device to at least some of the assigned sub-dialog devices; and aselecting device, which, functioning in response to the system messagesreceived from the assigned sub-dialog devices, selects a certain systemmessage and transmits the certain system message to the at least onefirst switching device.
 11. The dialog system as recited in claim 1,wherein at least one of a goal-directed dialog device and achat-oriented dialog device is used.
 12. The dialog system as recited inclaim 1, further comprising at least one second switching deviceconnected to the at least one terminal device and to a plurality of atleast one first switching devices, the at least one second switchingdevice including: a third device for relaying a user statement comingfrom the at least one second terminal device to at least some of theplurality of at least one first switching devices, and a fourth device,which, functioning in response to the system message received from therespective at least one first switching device, selects a certain systemmessage and transmits a certain system statement contained therein tothe at least one terminal device; the respective at least one firstswitching device being designed for relaying the certain system messageto the at least one second switching device.
 13. A dialog system for aman-machine interaction having cooperating dialog devices, comprising:at least one terminal device, where a user inputs a user statement, aplurality of interconnectible dialog devices, each dialog deviceincluding: an analyzing device for receiving and evaluating a userstatement generated by the at least one terminal device; a generatingdevice for generating a system message in dependence upon the analyzeduser statement; a decision device for relaying the analyzed userstatement for one of: to another dialog device and for relaying agenerated system message to the at least one terminal device independence upon the analyzed user statement; wherein the system messagegenerated by a dialog device, functioning in response to a userstatement, includes a system statement intended for the terminal device,an identification code identifying the dialog device, and/or anidentifier, the identifier signals whether or not a system statement hasbeen generated for a terminal device, or what quality the generatedsystem statement has; and the second device of the first switchingdevice has a detector device for capturing the identifier and theidentification code of a system message, a memory for storing a prioritylist of the assigned dialog devices, and a decision device, which usingthe stored priority list and the output signal from the detector deviceselects the system statement of a specific dialog device in order torelay it to the terminal device.